Brought the attributes module more inline with the jQuery style guidelines.

src/attributes.js

-var rclass = /[\n\t]/g;
+var rclass = /[\n\t]/g,
+	rspace = /\s+/,
+	rreturn = /\r/g,
+	rspecialurl = /href|src|style/,
+	rtype = /(button|input)/i,
+	rfocusable = /(button|input|object|select|textarea)/i,
+	rclickable = /^(a|area)$/i;
 
 jQuery.fn.extend({
 	attr: function( name, value ) {
-		return access(this, name, value, true, jQuery.attr);
+		return access( this, name, value, true, jQuery.attr );
 	},
 
 	addClass: function( value ) {
-		if(jQuery.isFunction(value)) {
+		if ( jQuery.isFunction(value) ) {
 			return this.each(function() {
 				jQuery(this).addClass( value.call(this) );
 			});
 		}
 
 		if ( value && typeof value === "string" ) {
-			var classNames = (value || "").split(/\s+/);
+			var classNames = (value || "").split( rspace );
 
 			for ( var i = 0, l = this.length; i < l; i++ ) {
 				var elem = this[i];
@@ -21,6 +27,7 @@ jQuery.fn.extend({
 				if ( elem.nodeType === 1 ) {
 					if ( !elem.className ) {
 						elem.className = value;
+
 					} else {
 						var className = " " + elem.className + " ";
 						for ( var c = 0, cl = classNames.length; c < cl; c++ ) {
@@ -37,14 +44,14 @@ jQuery.fn.extend({
 	},
 
 	removeClass: function( value ) {
-		if(jQuery.isFunction(value)) {
+		if ( jQuery.isFunction(value) ) {
 			return this.each(function() {
 				jQuery(this).removeClass( value.call(this) );
 			});
 		}
 
 		if ( (value && typeof value === "string") || value === undefined ) {
-			var classNames = (value || "").split(/\s+/);
+			var classNames = (value || "").split(rspace);
 
 			for ( var i = 0, l = this.length; i < l; i++ ) {
 				var elem = this[i];
@@ -56,6 +63,7 @@ jQuery.fn.extend({
 							className = className.replace(" " + classNames[c] + " ", " ");
 						}
 						elem.className = className.substring(1, className.length - 1);
+
 					} else {
 						elem.className = "";
 					}
@@ -82,20 +90,22 @@ jQuery.fn.extend({
 			var elem = this[0];
 
 			if ( elem ) {
-				if( jQuery.nodeName( elem, 'option' ) ) {
+				if ( jQuery.nodeName( elem, "option" ) ) {
 					return (elem.attributes.value || {}).specified ? elem.value : elem.text;
 				}
+
 				// We need to handle select boxes special
 				if ( jQuery.nodeName( elem, "select" ) ) {
 					var index = elem.selectedIndex,
 						values = [],
 						options = elem.options,
-						one = elem.type == "select-one";
+						one = elem.type === "select-one";
 
 					// Nothing was selected
 					if ( index < 0 ) {
 						return null;
 					}
+
 					// Loop through all the selected options
 					for ( var i = one ? index : 0, max = one ? index + 1 : options.length; i < max; i++ ) {
 						var option = options[ i ];
@@ -108,6 +118,7 @@ jQuery.fn.extend({
 							if ( one ) {
 								return value;
 							}
+
 							// Multi-Selects return an array
 							values.push( value );
 						}
@@ -117,7 +128,7 @@ jQuery.fn.extend({
 				}
 
 				// Everything else, we just grab the value
-				return (elem.value || "").replace(/\r/g, "");
+				return (elem.value || "").replace(rreturn, "");
 
 			}
 
@@ -128,25 +139,28 @@ jQuery.fn.extend({
 		if ( typeof value === "number" ) {
 			value += '';
 		}
+
 		var val = value;
 
 		return this.each(function(){
-			if(jQuery.isFunction(value)) {
+			if ( jQuery.isFunction(value) ) {
 				val = value.call(this);
+
 				// Typecast each time if the value is a Function and the appended
 				// value is therefore different each time.
-				if( typeof val === "number" ) {
+				if ( typeof val === "number" ) {
 					val += '';
 				}
 			}
 
-			if ( this.nodeType != 1 ) {
+			if ( this.nodeType !== 1 ) {
 				return;
 			}
+
 			if ( jQuery.isArray(val) && /radio|checkbox/.test( this.type ) ) {
 				this.checked = jQuery.inArray(this.value || this.name, val) >= 0;
-			}
-			else if ( jQuery.nodeName( this, "select" ) ) {
+
+			} else if ( jQuery.nodeName( this, "select" ) ) {
 				var values = jQuery.makeArray(val);
 
 				jQuery( "option", this ).each(function(){
@@ -156,6 +170,7 @@ jQuery.fn.extend({
 				if ( !values.length ) {
 					this.selectedIndex = -1;
 				}
+
 			} else {
 				this.value = val;
 			}
@@ -173,27 +188,31 @@ jQuery.each({
 
 	toggleClass: function( classNames, state ) {
 		var type = typeof classNames;
+
 		if ( type === "string" ) {
 			// toggle individual class names
 			var isBool = typeof state === "boolean", className, i = 0,
-				classNames = classNames.split( /\s+/ );
+				classNames = classNames.split( rspace );
+
 			while ( (className = classNames[ i++ ]) ) {
 				// check each className given, space seperated list
 				state = isBool ? state : !jQuery(this).hasClass( className );
 				jQuery(this)[ state ? "addClass" : "removeClass" ]( className );
 			}
+
 		} else if ( type === "undefined" || type === "boolean" ) {
 			if ( this.className ) {
 				// store className if set
 				jQuery.data( this, "__className__", this.className );
 			}
+
 			// toggle whole className
 			this.className = this.className || classNames === false ? "" : jQuery.data( this, "__className__" ) || "";
 		}
 	}
 }, function(name, fn){
 	jQuery.fn[ name ] = function(val, state){
-		if( jQuery.isFunction( val ) ) {
+		if ( jQuery.isFunction( val ) ) {
 			return this.each(function() { jQuery(this)[ name ]( val.call(this), state ); });
 		}
 
@@ -215,7 +234,7 @@ jQuery.extend({
 		
 	attr: function( elem, name, value ) {
 		// don't set attributes on text and comment nodes
-		if (!elem || elem.nodeType == 3 || elem.nodeType == 8) {
+		if ( !elem || elem.nodeType === 3 || elem.nodeType === 8 ) {
 			return undefined;
 		}
 
@@ -232,55 +251,58 @@ jQuery.extend({
 
 		// Only do all the following if this is a node (faster for style)
 		if ( elem.nodeType === 1 ) {
-
 			// These attributes require special treatment
-			var special = /href|src|style/.test( name );
+			var special = rspecialurl.test( name );
 
 			// Safari mis-reports the default selected property of a hidden option
 			// Accessing the parent's selectedIndex property fixes it
-			if ( name == "selected" && elem.parentNode ) {
+			if ( name === "selected" && elem.parentNode ) {
 				elem.parentNode.selectedIndex;
 			}
+
 			// If applicable, access the attribute via the DOM 0 way
 			if ( name in elem && notxml && !special ) {
 				if ( set ) {
 					// We can't allow the type property to be changed (since it causes problems in IE)
-					if ( name == "type" && /(button|input)/i.test(elem.nodeName) && elem.parentNode ) {
+					if ( name === "type" && rtype.test( elem.nodeName ) && elem.parentNode ) {
 						throw "type property can't be changed";
 					}
+
 					// browsers index elements by id/name on forms, give priority to attributes.
 					if( jQuery.nodeName( elem, "form" ) ) {
 						// convert the value to a string (all browsers do this but IE) see #1070
 						elem.setAttribute( name, "" + value );
+
 					} else {
 						elem[ name ] = value;
 					}
 				}
 
 				// browsers index elements by id/name on forms, give priority to attributes.
-				if( jQuery.nodeName( elem, "form" ) && elem.getAttributeNode(name) ) {
+				if ( jQuery.nodeName( elem, "form" ) && elem.getAttributeNode(name) ) {
 					return elem.getAttributeNode( name ).nodeValue;
 				}
+
 				// elem.tabIndex doesn't always return the correct value when it hasn't been explicitly set
 				// http://fluidproject.org/blog/2008/01/09/getting-setting-and-removing-tabindex-values-with-javascript/
-				if ( name == "tabIndex" ) {
+				if ( name === "tabIndex" ) {
 					var attributeNode = elem.getAttributeNode( "tabIndex" );
-					return attributeNode && attributeNode.specified
-						? attributeNode.value
-						: /(button|input|object|select|textarea)/i.test(elem.nodeName)
-							? 0
-							: /^(a|area)$/i.test(elem.nodeName) && elem.href
-								? 0
-								: undefined;
+
+					return attributeNode && attributeNode.specified ?
+						attributeNode.value :
+						rfocusable.test( elem.nodeName ) || rclickable.test( elem.nodeName ) && elem.href ?
+							0 :
+							undefined;
 				}
 
 				return elem[ name ];
 			}
 
-			if ( !jQuery.support.style && notxml && name == "style" ) {
+			if ( !jQuery.support.style && notxml && name === "style" ) {
 				if ( set ) {
 					elem.style.cssText = "" + value;
 				}
+
 				return elem.style.cssText;
 			}
 
@@ -288,10 +310,11 @@ jQuery.extend({
 				// convert the value to a string (all browsers do this but IE) see #1070
 				elem.setAttribute( name, "" + value );
 			}
-			var attr = !jQuery.support.hrefNormalized && notxml && special
+
+			var attr = !jQuery.support.hrefNormalized && notxml && special ?
 					// Some attributes require a special call on IE
-					? elem.getAttribute( name, 2 )
-					: elem.getAttribute( name );
+					elem.getAttribute( name, 2 ) :
+					elem.getAttribute( name );
 
 			// Non-existent attributes return null, we normalize to undefined
 			return attr === null ? undefined : attr;
@@ -299,6 +322,6 @@ jQuery.extend({
 
 		// elem is actually elem.style ... set the style
 		// Using attr for specific style information is now deprecated. Use style insead.
-		return jQuery.style(elem, name, value);
+		return jQuery.style( elem, name, value );
 	}
 });